User`s guide

Recommended Process for Latency Tuning
Chapter 12 Latency Tuning 107
Step 4: Optimize the network and transport layers
Depending on the results produced in steps 1, 2, and 3, optimize the
network and transport layers. Optimizing the network and transport layers,
may include, but is not limited to, these recommendations:
• Isolate any unnecessary TCP/IP traffic from the network.
• Choose smaller packets to reduce transit times through intermediate
networking devices, as most of these devices are store-and-forward.
• Increase the TCP/IP responsiveness to incoming/outgoing traffic by
choosing appropriate values for various TCP/IP timers, such as the
retransmission timer, the gratuitous ARP timer, and delayed
acknowledgment timer.
• Avoid the use of time-consuming encryption facilities.
Command options for optimizing network and transport layers
A major contributor to latency for the network and transport layers is
unnecessary retransmissions of data. The command-line interface has
several command options to help you reduce these unnecessary
retransmissions. Most of these options are available through the
command-line interface only, and not the Web user interface.
For complete descriptions of these commands and options, see the Digi
One and PortServer TS Family Command Reference.
There are several considerations for using these latency-related command
options:
• Changing the options from their defaults may violate RFCs.
• Decrementing the values for these options increases the amount of
network activity, for example, there will be increased retransmissions.
• For a peer-to-peer application, you need to consider both sides of the
connection and how options are set. For example, if the setting for the
“rto_min” option for the Digi device is set to a value that is less than the
setting for the “delayed_ack” option for the other side of the connection,
then there will be a forced retransmission of every packet of data. For a
master-slave application, this consideration does not apply.